The dramatic accident involving ammonium nitrate (AN) that took place at Toulouse in September 2001 has once again focused attention on the hazards pertaining to chemical incompatibility in an industrial environment. To complete the experimental results, a detailed theoretical study was performed to better understand the involved mechanisms, considering the reaction between ammonium nitrate and the sodium salt of dichloroisocyanuric acid (SDIC). Starting from theoretical results obtained for the pure reactants, the gas-phase decomposition mechanism of the mixture was investigated and fully characterized by means of density functional theory (DFT) calculations. Beyond the complete characterization, in terms of intermediate structures and energies, of the decomposition pathways, the results evidenced the role of water in catalyzing the decomposition reaction, through a significant decrease of the activation energy of the rate-determining step. These results, in qualitative agreement with the calorimetric experiments, pointed out the instability of the ANSDIC wet mixture and the underpinning incompatibility mechanism between these two chemicals.

Sensors are important devices for alerting to the presence of leaked hydrogen in any application involving the production, storage, or use of hydrogen. Key missions for the sensor test laboratories in the U.S. Department of Energy, National Renewable Energy Laboratory and in the European Commission Joint Research Centre, Institute for Energy and Transport are to assure the availability and proper use of hydrogen safety sensors. As an integral element in a safety system, sensor performance should not be compromised by operational parameters. For example, safety sensors may be required to operate at reduced oxygen levels relative to air, such as that which would exist for nitrogen purges. Some sensor platforms are amenable for anaerobic operation, whereas other platforms will be deactivated and possible permanently altered with anaerobic operation. The NREL and JRC sensors laboratories assessed the ability of a number of sensor platforms to detect hydrogen under conditions of varying oxygen concentration. The performance of three common hydrogen sensor platforms, the thermal conductivity sensor, combustible gas sensor, and a palladium thin-film (metallic resistor) sensor, to operate under anaerobic conditions is presented. Copyright (C) 2012, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.

In August 1992, four farm workers in Minnesota died in two separate incidents after entering manure waste pits: two were poisoned by hydrogen sulfide gas, and two were asphyxiated. The Minnesota Fatality Assessment and Control Evaluation (FACE) program was notified of the incidents by the state Occupational Safety and Health Administration and the Minnesota Farming Health Project, respectively. This report summarizes the investigations of these two incidents by the Minnesota FACE program and CDC's National Institute for Occupational Safety and Health (NIOSH) FACE personnel.

The use of hydrogen as an energy carrier for road transport appears to be an optimal solution for the reduction of greenhouse gas emissions. Nevertheless, the development of this technology depends on the growth and diffusion of production, storage and refuelling infrastructures together with accurate risk analyses to appropriately design the safety and management systems used in these plants. Moreover, to improve safety standards, it is also important to focus attention on the estimation of hazards related to human factors, as this is one of the major causes leading to accidental events, especially in complex industrial technology. The paper reports a case study relevant to operator errors that occur during maintenance procedures on safety venting devices in refuelling station hydrogen storage systems performed using first- and second-generation Human Rate Assessment (HRA) techniques. HEART (Human Error Assessment and Reduction Technique) methodology, a first-generation HRA method, which was modified on the basis of the fuzzy set concept, was employed to evaluate the probability of erroneous actions. The obtained results have been compared with results obtained using CREAM (second-generation) methodology. The critical analyses of the obtained results have also allowed to provide procedural recommendations and suggestions regarding safety equipment and procedures which can be adopted to reduce the risk of accidents. Copyright (c) 2012, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.

The results of hydrogen-induced cracking, hydrogen stress corrosion cracking (HSCC) and HSCC tests under cathodic protection obtained on the normalised medium/high strength steels for marine applications, ASA 56, ASA F56 and ASA F60, are reported. Fatigue precracked WOL specimens were loaded at room temperature and simultaneously exposed to synthetic seawater, saturated or not by hydrogen sulphide (H2S) and at two initial pH values (pH = 1; pH = 3). Here indications are given on the types of mechanisms controlling the damaging, the comparison of the values of the crack propagation threshold stress intensity factor in air and in corrosive media, the influence of the presence of H2S, the role of inclusions and of their plane's orientation, the relationship between the damaging phenomena, the effect of the cathodic protection.

At present, the hydrogen vehicles technology appears to have future Prospective for reduction in greenhouse gas emissions. Nevertheless, the development of such a technology requires appropriate infrastructures for production, Storage and refuelling stages in a refuelling station. This one presents safety challenges due to the hydrogen chemicophysical characteristics. So, to avoid hazards, it is necessary to implement safety practices that, if early adopted in the development of a fuelling station project, can allow very low impact, safety being incorporated in the project itself. However, a drawback is the not sufficient experience and the scarcity of the relevant data collection. To deepen studies about the risk in the above mentioned field, in this paper, for the moment, safety analyses of a high-pressure storage equipment in hydrogen gas refuelling station have been carried out by the integrated use of FMEA, HAZOP and FTA techniques. The work is intended to assess if the refuelling station design taken into consideration is safe enough, at least from the occurrence frequency point of view, as well to constitute a basis for further more refined studies which also consider the consequences aspects, allowing the plant risk assessment. (C) 2009 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved.

The use of hydrogen as an energy carrier for the future is conditioned by its safety. Hydrogen is commonly and incorrectly perceived as being a more dangerous gas than methane, since the latter is widely used and thus considered to be acceptable. The paper analyses deflagrations of H-2/air and CH4/air mixtures at low concentrations (close to the lower flammability limits) and, in particular, focuses on the phenomenology and dangerous aspects of this kind of combustion. The related possible accidents involve closed environments (garages, laboratories, service rooms, internal volumes of buses and cars, etc.) where ignition sources are present. In these cases, combustion probably takes place as soon as the fuel concentration reaches the lower flammability limit. Hydrogen and methane are compared on the basis of (1) their general energetic characteristics, (2) a theoretical examination of the main parameters related to the combustion phenomenon, and (3) the experimental results of the LargeView2 apparatus, where more than 300 deflagration tests were made with both gases in a vented multi-compartment container. (c) 2004 Elsevier Ltd. All rights reserved.

The physics of hydrogen release from compressed storage vessels is investigated for flow conditions corresponding to a subsonic turbulent jet venting into atmosphere at a Mach number similar to 0.3 using large eddy simulations (LES) and particle image velocimetry (PIV) measurements. A major focus of the work is investigation of the dynamic features of the flow and mixing processes by analyzing the detailed instantaneous data available from LES. Simulations are first conducted for a helium jet with flow parameters corresponding closely to hydrogen jet release at low Mach number in order to allow direct comparison with Ply measurements. The simulations and measurements are consistent, and show that though exact self-similarity of the turbulent jet is not achieved due to buoyancy effects, the normalized averaged velocity and concentration profiles collapse reasonably well and can be approximated by a Gaussian distribution. Analysis of the instantaneous concentration fields shows that, due to the complex dynamics of the jet, which includes flapping and vortex shedding, concentration levels above the flammability threshold occur intermittently in regions where average concentrations are low. The spatial extent of regions where flammability thresholds are exceeded is nearly twice as large when considering transient effects compared to the mean (time-averaged) flow; the possible implications for safety guidelines are important. LES results are also presented for a hydrogen jet during the transient phase following the onset of release. Compared to the stationary jet flow, the radial extent of concentration above the flammability threshold is found to increase by similar to 30%2during transients as a result of the strong vortex ring that forms when the hydrogen jet penetrates stationary ambient air. (c) 2010 Professor T. Nejat Veziroglu. Published by Elsevier Ltd. All rights reserved.